new to these forums and KiCad. I am a software engineer who got fascinated with the world of electronics and set of on my first large scale project, creating a 3+1 game for my kid.
It’s features a set of 7 LED arcade illuminated buttons + 1 large green one, 3 rotary encoders with 10LED bars and an LED each, and a few other components…
Games are simple:
Buttons play tunes based on a program that lights up the right button to play the tune.
Buttons and rotary encoders play with my houses hue lights
Added an adafruit 8led bar on a motor to create some light show, controlled by the encoders and buttons for patterns and colors.
Anyway, don’t wanna bore you with this, I set off to create the circuit diagram to learn KiCad and figure out any issues ahead of time (turns out i did and was a very helpful and rewarding journey).
I am looking for feedback on quite a few areas:
My overall KiCad usage and design patterns.
Due to the amount of inputs and outputs, if I chose the right way to manage them with Shift Registers.
Overall circuit feedback.
As I am a new user I think I will not be able to attach multiple images, so I’ve posted all the diagram and a few in-progress project photos on postimages service, use this link:
I won’t comment on the circuit characteristics, but on your drawing style.
You get plus points for using hierachical sheets in a sensible way. How to partition a circuit correctly is not easy.
You get minus points for using portrait format for the schematic. For readability, schematics are always left-to-right (inputs-to-outputs).
A suggestion: your circuit really calls for using bus connections. Following a line is much easier than searching for some alphanumeric label.
Generally: “Chapeau!”, for a first attempt it’s good.
In my opinion you didn’t use enough capacitors.
Whenever in our (firm) history we had a problem with something works but from time to time there are problems (like EPROM emulator giving corrupted byte ones per 3 million reads) the reason was a lack of capacitor at right place.
Add 100n to each IC as close (at PCB) as possible to it. You need not to show at schematic both wires of capacitor going to IC pins. Just place capacitor near VCC pin and connect its other side to GND.
And also VCC up and GND down. You have it opposite sometimes.
I will reinforce Piotr’s remarks. When you lay out your pcb, place power supply rail bypass ceramic chip capacitors at all of the ICs as close as possible, as a first step. For some beginners, supply rail bypassing is an afterthought or no thought. That is an error… I like to bypass with an 0603 chip as close as possible to the IC. If you need more capacitance than can fit in an 0603, place the larger chip capacitor outside the smaller one so it is a little further away.
As a standard I use 0603 capacitors but I use 100n 0402 at each IC power pin. The reason for using 0402 was that I have one at each side of AtXmega chips (along side as there are VCC, GND pin pairs) and 0603 are huge and interfere with adjacent pin tracks.
Hi @thanpolas
Total capacitance is not the problem.
When you have finished assembling the Christmas present, spend a little time googling “bypass capacitors” or “decoupling capacitors”.
Typically at any power rail (+5V, VCC, I don’t look at your schematic now) you should have one bigger capacitor (like 100uF electrolytic) anywhere and 100nF at each IC. These 100nF will be better installed if they will be connected directly to VCC and GND IC pins - diagonally.
Capacitance sum can be important only if you use Low Drop Voltage regulators as they tend to be unstable (their data sheets define stability region dependent of load capacitance).
At picture from first post I see power modules. Surprising is that there are no capacitors at their inputs and outputs. I just supposed capacitors are inside these modules.
